style: suppress UI5 ObjectPageSubSection mouse-focus outline

[maximilianbraun]

Summary

UI5's ObjectPageSubSection paints a cyan focus outline via the plain :focus pseudo (not :focus-visible), which framed the entire graph subsection in cyan whenever pointer focus landed there. Suppress the outline only for mouse-focus by scoping the override to :focus:not(:focus-visible); keyboard-focus still draws the cue UI5 ships.

What changed

• src/index.css — add a small block that removes outline / box-shadow from ui5-object-page-sub-section:focus:not(:focus-visible) (and the equivalent shadow-DOM part). The :not(:focus-visible) guard preserves keyboard a11y on all other subsections.

Why

When you click into the graph subsection, the whole frame lit up cyan. The active tab already conveys which subsection is selected, so the outline was visual noise — and worse, it stayed up during graph interaction.

Initial commit was a blanket :focus suppression, which also stripped the keyboard-navigation cue. Second commit tightened it to :focus:not(:focus-visible) so:

• Pointer-focus (clicking into a section): outline removed.
• Keyboard-focus (Tab to a section): outline preserved.

This is a temporary blanket suppression across all ObjectPageSubSections, not just the graph. A follow-up should attach a data-subsection="graph" attribute and scope this rule to that selector only — but that's a UI5/JSX-side change that's out of scope here.

Test plan

• npm run type-check
• npm run lint
• npm run test:vi
• Open an MCP page, click into the graph subsection: confirm no cyan frame appears.
• Same page, press Tab repeatedly until focus lands on a subsection header: confirm the UI5 keyboard-focus cue still draws.
• Visually sanity-check other ObjectPage subsections (Members, ComponentsSelection, etc.) for unintended outline regressions.